The aims of this project are 1) to determine the relationship between pulmonary lymph flow rate (QL) and the basic factors which cause lymph flow; 2) to determine the effects of maximizing QL upon the ability of the lung to resist edema formation. We consider the basic factors which cause lymph flow to be tissue fluid hydrostatic pressure (pt), the outflow pressure from the lymph vessels (Po), the lymph vessel hydraulic resistance (RL) and the pressure (Pp) which is generated by the lymph "pumping" mechanism. Thus QL = (Pt + Pp - Po)/RL. We will estimate all of the terms in this equation by cannulating a small hilar lymph vessel from the continuously weighed, intact lower left lobe of dog lungs. We will measure QL at several different Po's. From the linear relationship between QL and Po, we will estimate Pp, Pt, and RL. We will estimate Pp, Pt, and RL after elevating capillary pressure to various levels and we will estimate the amount of edema fluid which accumulates from the weight recording. We will also estimate Pp, Pt, and RL at various respiratory rates and pressures. Thus we will be able to determine how Pp, Pt, and RL vary under various conditions and we can determine how these factors affect QL. We will supplement this information with morphological examinations of lung tissue. From this we may be able to establish relatonship between QL and the site of edema fluid accumulation. We will use the information obtained in all experiments to maximize QL and then we will determine what effect this has on the ability of the lung to resist edema. Information from this study could be used to increase QL in patients with pulmonary edema. This could prevent further edema as well as help to remove edema fluid which has already accumulated.